12v in & OUT charger (for handheld VHF)

mogmog2

mogmog2

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Hi, I have a handheld VHF ('obsolete' Silva S12) which takes a 12v input to charge. Could I just tap into the boat's supply? I think it would be prudent to include a little something to protect it - other manufacturers have cigarette socket chargers but don't list the specs but the circuitry in them can't be much as it fits in the plug body.

Generic 12v in 12v out chargers seem to be uncommon.

Can any electronics gurus advise? I was thinking of part of a charger - something like this (everything after the rectifier)?
Many thanks
http://www.zen22142.zen.co.uk/Circuits/Power/nicad_simulation.png
 
mogmog2 said:
Hi, I have a handheld VHF ('obsolete' Silva S12) which takes a 12v input to charge. Could I just tap into the boat's supply? I think it would be prudent to include a little something to protect it - other manufacturers have cigarette socket chargers but don't list the specs but the circuitry in them can't be much as it fits in the plug body.

Generic 12v in 12v out chargers seem to be uncommon.

Can any electronics gurus advise? I was thinking of part of a charger - something like this (everything after the rectifier)?
Many thanks
http://www.zen22142.zen.co.uk/Circuits/Power/nicad_simulation.png
Click to expand...

They usually come with a charge cable .... which is just a plain cable with the suitable plug on one end which fits the radio/cradle and a suitable cigarette plug on the other which connects to the 12V battery, usually with a small fuse (10A max but 1A probably fine for a dedicated cable) inside the cigarette plug.

Richard
 
mogmog2 said:
Hi, I have a handheld VHF ('obsolete' Silva S12) which takes a 12v input to charge. Could I just tap into the boat's supply? I think it would be prudent to include a little something to protect it - other manufacturers have cigarette socket chargers but don't list the specs but the circuitry in them can't be much as it fits in the plug body.

Generic 12v in 12v out chargers seem to be uncommon.

Can any electronics gurus advise? I was thinking of part of a charger - something like this (everything after the rectifier)?
Many thanks
http://www.zen22142.zen.co.uk/Circuits/Power/nicad_simulation.png
Click to expand...

Based on the limited information in the owners manual I think I would simply connect to the boat's 12 volt supply!
 
I've got one with the direct plug to socket and no problems, check ebay. Given the age, you probably want to replace the 10AAA NiMh batteries in it. I did about 7 years ago and need to do so again.
 
RichardS - I haven't got the charge cable. Or a cradle - charging is through a 3.4mm socket under a flap. Or a cigarette socket on the boat and other than knowing the engine starts, the rest of the boat electrics are pretty unknown as yet

CTVA, Yes they would definitely benefit from being changed -hope to do it before the trip, but may not get chance hence trying to get power available. I did look inside some while ago & IIRC they are tagged & need soldering?

VicS, I thought the manual was rather limited too, in pretty much every way.

Thanks everyone for the confirmation.
I'll try that direct connection with a fuse. If it goes phut I'll be bounced into the modern age & need a new one, but am buying lots of stuff at present so a new handheld VHFis not planned any time soon.
 
Blimey: There is almost nothing out there on this radio & you found that! I have the mains unit but thanks very much for your effort.
 
mogmog2 said:
...CTVA, Yes they would definitely benefit from being changed -hope to do it before the trip, but may not get chance hence trying to get power available. I did look inside some while ago & IIRC they are tagged & need soldering?..
Click to expand...

Yes, but quit simple and quick. Well worth it.
 
If the radio has 10x NiMH or NiCad batteries then just 12v will not charge them. The battery voltage will be 12v. They will need something closer to 15v to push current into them. Probably charge oK if slow on a 12v battery on charge ie abut 14v. You would want to check with an amp meter for actual charge current. AA sized NiMH will typically be charged at about 100ma for 14hours. Don't leave on permanent charge as they can overheat and be damaged. You can recharge faster but don't forget to turn off charger.
The formular for charge current is usually Milliamp hour rating divided by 10 but charged for 14 hrs to make up for inefficiencies in charging. That circuit referred to originally is for current limited charge for 9v output. With 12v in it would be limited to about 11 v output if adjusted to do so. I think what you will need for charging from boat battery is a boost converter to take whatever battery voltage you have up to around 15v then feed the radio with a series current limiting resistor to set charge current. All a bit complicated. Perhaps buy a new set of batteries and battery holder to set up an external charger, then fit batteries when charged. olewill
 
William_H said:
If the radio has 10x NiMH or NiCad batteries then just 12v will not charge them. The battery voltage will be 12v. They will need something closer to 15v to push current into them. Probably charge oK if slow on a 12v battery on charge ie abut 14v. You would want to check with an amp meter for actual charge current. AA sized NiMH will typically be charged at about 100ma for 14hours. Don't leave on permanent charge as they can overheat and be damaged. You can recharge faster but don't forget to turn off charger.
The formular for charge current is usually Milliamp hour rating divided by 10 but charged for 14 hrs to make up for inefficiencies in charging. That circuit referred to originally is for current limited charge for 9v output. With 12v in it would be limited to about 11 v output if adjusted to do so. I think what you will need for charging from boat battery is a boost converter to take whatever battery voltage you have up to around 15v then feed the radio with a series current limiting resistor to set charge current. All a bit complicated. Perhaps buy a new set of batteries and battery holder to set up an external charger, then fit batteries when charged. olewill
Click to expand...

According to the owners manual the internal battery is 9.6 volts, which is presumably 8 cells

http://www.nexusmarine.se/wp-content/uploads/2011/12/s12_eng.pdf
 
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